I have exactly the same problem with mine. I have two bags from hay expertd (cant think which off the top of my head), i sometimes hide herby treats in the hay, Poppy will forage through to get the bits & and I hope sometimes eats a bit of hay when doing so.
I feel your pain, I have spent a lot of money trying to get Poppy to eat hay, i feel im fighting a losing battle. She loves readigrass but it gives her excess ceacs (which she has everyday anyway due to lack of hay but readigrass seems to make it even worse).
Good luck.